Shellacked in Seattle: Seahawks rout 49ers, 42-13

SEATTLE — The home crowd was deafening, but the message sent by the home team Sunday night was even more ear-splitting: Look out for us in January.

In a much-anticipated meeting between bitter NFC West rivals, the Seahawks humiliated the 49ers, 42-13, on Sunday night, handing Jim Harbaugh the worst loss of his 31-game tenure in San Francisco on his 49th birthday.

Despite the drubbing, the 49ers (10-4-1) still have a half-game lead on the Seahawks (10-5) for the division title and can clinch the NFC West crown with a win over visiting Arizona (5-10) on Sunday. They slipped to the No. 3 seed in the NFC behind Green Bay (11-4) and won’t have a first-round bye if the Packers win at Minnesota in their regular-season finale.

After Sunday night’s rout before a typically raucous crowd at CenturyLink Field, the 49ers are surely hoping their postseason calendar doesn’t include another date with the Seahawks, who have won their past three games by a combined score of 150-30.

Two months after a 13-6 loss in San Francisco, it took Seattle 72 seconds to top that Week 7 point total as running back Marshawn Lynch rumbled 24 yards for a tone-setting touchdown on their second offensive play.

The Seahawks led 21-0 just 55 seconds into the second quarter, didn’t punt until the third quarter and held a 35-6 edge with 18 minutes left. The 49ers hadn’t allowed 35 points since a 45-10 loss to the Falcons on Oct. 10, 2009.

Their defensive collapse coincided with the loss of All-Pro defensive tackle Justin Smith, who had his streak of 185 consecutive starts dating back to 2001 snapped because of an elbow injury. Smith missed the majority of the second half of San Francisco’s 41-34 win at New England on Dec. 16 and the statistical dropoff since he was sidelined is startling.

In their past six quarters, the 49ers have allowed 48 first downs, 73 points and 753 yards.

On Lynch’s first-quarter touchdown run, he ran past Smith’s replacement, four-year veteran Ricky Jean Francois, en route to a 26-carry, 111-yard performance, his third straight 100-yard game against the 49ers.

This loss, however, was a total team effort.

On offense, quarterback Colin Kaepernick, who called two time outs with the play clock ticking down and was flagged for two delay-of-game penalties in the first half, had the lowest rating (72.0) of his six-start career.

The special teams also faltered. Trailing 14-0 early in the third quarter, David Akers had a 21-yard field-goal attempt blocked by Seattle defensive end Red Bryant and the loose ball was returned 90 yards for a touchdown by cornerback Richard Sherman.

Sherman, who played for Harbaugh at Stanford, had referred to his old coach as a “bully” earlier this season. And Sherman, who added a fourth-quarter interception in the end zone, and wide receiver Doug Baldwin, another Harbaugh protégé, played key roles in pushing the 49ers around.

Baldwin (4 catches, 53 yards) scored Seattle’s final two touchdowns on passes of 4 and 6 yards from rookie quarterback Russell Wilson, who has thrown 16 touchdowns and three interceptions in his past eight starts.

The physical game took a toll on the 49ers, who lost tight end Vernon Davis to a concussion in the first quarter after he took a violent hit from safety Cam Chancellor. In the third quarter wide receiver Mario Manningham, who had missed the previous two games with a shoulder injury, sustained what appeared to be a potential serious injury to his left knee.

Photo: Jordan Stead / Special to the Chronicle

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Jim Harbaugh, head coach of the San Francisco 49ers, looks on in disappointment after a score by the Seahawks during the first half of a game Sunday, Dec. 23, 2012, at CenturyLink Field in Seattle, WA. Seahawks led 28-6 at the half. less

Jim Harbaugh, head coach of the San Francisco 49ers, looks on in disappointment after a score by the Seahawks during the first half of a game Sunday, Dec. 23, 2012, at CenturyLink Field in Seattle, WA. ... more

Photo: Jordan Stead / Special to the Chronicle

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Seattle Seahawks' Doug Baldwin (89) comes down with a touchdown catch past the defense of San Francisco 49ers' Carlos Rogers (22) in the second half of an NFL football game, Sunday, Dec. 23, 2012, in Seattle. less

Seattle Seahawks' Doug Baldwin (89) comes down with a touchdown catch past the defense of San Francisco 49ers' Carlos Rogers (22) in the second half of an NFL football game, Sunday, Dec. 23, 2012, in ... more

Photo: Elaine Thompson / Associated Press

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Michael Crabtree, right, of the San Francisco 49ers, tumbles over Seahawk Bobby Wagner, left, during the first half of a game Sunday, Dec. 23, 2012, at CenturyLink Field in Seattle, WA.

Michael Crabtree, right, of the San Francisco 49ers, tumbles over Seahawk Bobby Wagner, left, during the first half of a game Sunday, Dec. 23, 2012, at CenturyLink Field in Seattle, WA.

Photo: Jordan Stead / Special to the Chronicle

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Marshawn Lynch, left, of the Seattle Seahawks, pushes through 49er defense during the first half of a game Sunday, Dec. 23, 2012, at CenturyLink Field in Seattle, WA.

Marshawn Lynch, left, of the Seattle Seahawks, pushes through 49er defense during the first half of a game Sunday, Dec. 23, 2012, at CenturyLink Field in Seattle, WA.

Photo: Jordan Stead / Special to the Chronicle

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Anthony McCoy, left, of the Seattle Seahawks, makes a touchdown catch during the first half of the Seahawks and 49ers game Sunday, Dec. 23, 2012, at CenturyLink Field in Seattle, WA. The Seahawks led 28-6 at the half. less

Anthony McCoy, left, of the Seattle Seahawks, makes a touchdown catch during the first half of the Seahawks and 49ers game Sunday, Dec. 23, 2012, at CenturyLink Field in Seattle, WA. The Seahawks led 28-6 at ... more

Photo: Jordan Stead / Special to the Chronicle

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Robert Turbin #22 of the Seattle Seahawks runs for yards after the catch against Patrick Willis #52 of the San Francisco 49ers at Qwest Field on December 23, 2012 in Seattle, Washington.

Robert Turbin #22 of the Seattle Seahawks runs for yards after the catch against Patrick Willis #52 of the San Francisco 49ers at Qwest Field on December 23, 2012 in Seattle, Washington.

Photo: Otto Greule Jr / Getty Images

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Michael Crabtree, right, of the San Francisco 49ers, glances at the scoreboard after a touchdown for the Seahawks during the first half of a game Sunday, Dec. 23, 2012, at CenturyLink Field in Seattle, WA.

Michael Crabtree, right, of the San Francisco 49ers, glances at the scoreboard after a touchdown for the Seahawks during the first half of a game Sunday, Dec. 23, 2012, at CenturyLink Field in Seattle, WA.

Photo: Jordan Stead / Special to the Chronicle

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San Francisco 49ers quarterback Colin Kaepernick stands on the sideline in the first half of an NFL football game against the Seattle Seahawks, Sunday, Dec. 23, 2012, in Seattle.

San Francisco 49ers quarterback Colin Kaepernick stands on the sideline in the first half of an NFL football game against the Seattle Seahawks, Sunday, Dec. 23, 2012, in Seattle.

Photo: John Froschauer / Associated Press

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San Francisco 49ers' Vernon Davis, left, is hit by Seattle Seahawks' Kam Chancellor, right during a reception attempt in the first half of an NFL football game, Sunday, Dec. 23, 2012, in Seattle.

San Francisco 49ers' Vernon Davis, left, is hit by Seattle Seahawks' Kam Chancellor, right during a reception attempt in the first half of an NFL football game, Sunday, Dec. 23, 2012, in Seattle.

Photo: John Froschauer / Associated Press

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San Francisco 49ers' Vernon Davis, left, is hit by Seattle Seahawks' Kam Chancellor, right, during a reception attempt in the first half of an NFL football game, Sunday, Dec. 23, 2012, in Seattle.

San Francisco 49ers' Vernon Davis, left, is hit by Seattle Seahawks' Kam Chancellor, right, during a reception attempt in the first half of an NFL football game, Sunday, Dec. 23, 2012, in Seattle.

Photo: John Froschauer / Associated Press

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Patrick Willis #52 of the San Francisco 49ers intercepts a pass in the first half against Paul McQuistan #67 of the Seattle Seahawks at Qwest Field on December 23, 2012 in Seattle, Washington.

Patrick Willis #52 of the San Francisco 49ers intercepts a pass in the first half against Paul McQuistan #67 of the Seattle Seahawks at Qwest Field on December 23, 2012 in Seattle, Washington.

Photo: Otto Greule Jr / Getty Images

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San Francisco 49ers' Frank Gore (21) rushes against Seattle Seahawks' Malcolm Smith (53) in the first half of an NFL football game, Sunday, Dec. 23, 2012, in Seattle.

San Francisco 49ers' Frank Gore (21) rushes against Seattle Seahawks' Malcolm Smith (53) in the first half of an NFL football game, Sunday, Dec. 23, 2012, in Seattle.

Photo: Elaine Thompson / Associated Press

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Seattle Seahawks' Anthony McCoy reacts after scoring against the San Francisco 49ers late in the first half of an NFL football game, Sunday, Dec. 23, 2012, in Seattle.

Seattle Seahawks' Anthony McCoy reacts after scoring against the San Francisco 49ers late in the first half of an NFL football game, Sunday, Dec. 23, 2012, in Seattle.

Photo: Elaine Thompson / Associated Press

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Seattle Seahawks' Kam Chancellor (31) hits San Francisco 49ers' Vernon Davis on a reception attempt in the first half of an NFL football game, Sunday, Dec. 23, 2012, in Seattle. (AP Photo/Elaine Thompson) less

Seattle Seahawks' Kam Chancellor (31) hits San Francisco 49ers' Vernon Davis on a reception attempt in the first half of an NFL football game, Sunday, Dec. 23, 2012, in Seattle. (AP Photo/Elaine ... more

Photo: Associated Press

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Seattle Seahawks' Marshawn Lynch (24) runs for a touchdown against the San Francisco 49ers in the first half of an NFL football game, Sunday, Dec. 23, 2012, in Seattle.

Seattle Seahawks' Marshawn Lynch (24) runs for a touchdown against the San Francisco 49ers in the first half of an NFL football game, Sunday, Dec. 23, 2012, in Seattle.

Photo: John Froschauer / Associated Press

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Russell Okung #76 and Marshawn Lynch #24 of the Seattle Seahawks celebrate after Lynch scored a 24-yard rushing touchdown in the first quarter against the San Francisco 49ers at Qwest Field on December 23, 2012 in Seattle, Washington. less

Russell Okung #76 and Marshawn Lynch #24 of the Seattle Seahawks celebrate after Lynch scored a 24-yard rushing touchdown in the first quarter against the San Francisco 49ers at Qwest Field on December 23, ... more

Photo: Otto Greule Jr / Getty Images

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Paul McQuistan #67 and Marshawn Lynch #24 of the Seattle Seahawks celebrate after Lynch scored a 24-yard rushing touchdown in the first quarter against the San Francisco 49ers at Qwest Field on December 23, 2012 in Seattle, Washington. less

Paul McQuistan #67 and Marshawn Lynch #24 of the Seattle Seahawks celebrate after Lynch scored a 24-yard rushing touchdown in the first quarter against the San Francisco 49ers at Qwest Field on December 23, ... more

Photo: Otto Greule Jr / Getty Images

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San Francisco 49ers head coach Jim Harbaugh tosses the football prior to the start of an NFL football game against the Seattle Seahawks, Sunday, Dec. 23, 2012, in Seattle.

San Francisco 49ers head coach Jim Harbaugh tosses the football prior to the start of an NFL football game against the Seattle Seahawks, Sunday, Dec. 23, 2012, in Seattle.

Photo: Elaine Thompson / Associated Press

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Seattle Seahawks' Kam Chancellor warms up in the rain prior to an NFL football game against the San Francisco 49ers, Sunday, Dec. 23, 2012, in Seattle.

Seattle Seahawks' Kam Chancellor warms up in the rain prior to an NFL football game against the San Francisco 49ers, Sunday, Dec. 23, 2012, in Seattle.

Photo: Elaine Thompson / Associated Press

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Seattle Seahawks Sea Gals cheerleaders perform in holiday attire in the first half of an NFL football game, Sunday, Dec. 23, 2012, in Seattle.

Seattle Seahawks Sea Gals cheerleaders perform in holiday attire in the first half of an NFL football game, Sunday, Dec. 23, 2012, in Seattle.

Photo: Elaine Thompson / Associated Press

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San Francisco 49ers quarterback Colin Kaepernick calls to his team in the first half of an NFL football game against the Seattle Seahawks, Sunday, Dec. 23, 2012, in Seattle.

San Francisco 49ers quarterback Colin Kaepernick calls to his team in the first half of an NFL football game against the Seattle Seahawks, Sunday, Dec. 23, 2012, in Seattle.

Photo: Elaine Thompson / Associated Press

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Russell Wilson #3 of the Seattle Seahawks looks to pass in the first half against the San Francisco 49ers at Qwest Field on December 23, 2012 in Seattle, Washington.

Russell Wilson #3 of the Seattle Seahawks looks to pass in the first half against the San Francisco 49ers at Qwest Field on December 23, 2012 in Seattle, Washington.

Photo: Otto Greule Jr / Getty Images

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Marshawn Lynch #24 of the Seattle Seahawks scores a 24-yard rushing touchdown in the first quarter against the San Francisco 49ers at Qwest Field on December 23, 2012 in Seattle, Washington.

Marshawn Lynch #24 of the Seattle Seahawks scores a 24-yard rushing touchdown in the first quarter against the San Francisco 49ers at Qwest Field on December 23, 2012 in Seattle, Washington.

Photo: Otto Greule Jr / Getty Images

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Richard Sherman #25 of the Seattle Seahawks returns a blocked field goal attempt 90 yards for a touchdown in the second quarter against the San Francisco 49ers at Qwest Field on December 23, 2012 in Seattle, Washington. less

Richard Sherman #25 of the Seattle Seahawks returns a blocked field goal attempt 90 yards for a touchdown in the second quarter against the San Francisco 49ers at Qwest Field on December 23, 2012 in Seattle, ... more

Photo: Otto Greule Jr / Getty Images

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Seattle Seahawks' Marshawn Lynch (24) scores a touchdown as San Francisco 49ers' Carlos Rogers, left, and Tarell Brown, center, look on in the first half of an NFL football game, Sunday, Dec. 23, 2012, in Seattle. less

Seattle Seahawks' Marshawn Lynch (24) scores a touchdown as San Francisco 49ers' Carlos Rogers, left, and Tarell Brown, center, look on in the first half of an NFL football game, Sunday, Dec. 23, 2012, in ... more

Photo: Elaine Thompson / Associated Press

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Seattle Seahawks' Marshawn Lynch scores his second touchdown of the game against the San Francisco 49ers in the first half of an NFL football game as San Francisco 49ers' Tarell Brown looks on at right, Sunday, Dec. 23, 2012, in Seattle. less

Seattle Seahawks' Marshawn Lynch scores his second touchdown of the game against the San Francisco 49ers in the first half of an NFL football game as San Francisco 49ers' Tarell Brown looks on at right, ... more

Photo: Elaine Thompson / Associated Press

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Neal Nilsen, of Federal Way, Wash., is shown dressed as Santa in Seattle Seahawks colors as he throws candy to fans prior to an NFL football game against the San Francisco 49ers, Sunday, Dec. 23, 2012, in Seattle. less

Neal Nilsen, of Federal Way, Wash., is shown dressed as Santa in Seattle Seahawks colors as he throws candy to fans prior to an NFL football game against the San Francisco 49ers, Sunday, Dec. 23, 2012, in ... more